1. Field of the Invention
The present invention relates to a key structure, and in particular to a thin key structure capable of reducing the height of the key structure to facilitate steady operation at the important machine—human interface for data entry—the keyboard or keypad.
2. Description of Related Art
With the advancement of technology, electronic products such as personal computers, notebook computers and mobile phones are widely used in our daily life. Further, the range to which these electronic products can be applied becomes constantly larger. For easy carrying, electronic products are made to be more compact. As a result, it is an important issue for the manufacturers in this art to reduce the thickness of the keyboard associated with such compact electronic products as much as possible. FIG. 1 and FIG. 2 are exploded perspective views showing the conventional key structure from different viewing angles. The conventional key structure includes a base 10, an elastic piece 30 and a keycap 50. FIG. 3 is an assembled cross-sectional view showing the conventional key structure of FIGS. 1 and 2. FIG. 4 is a cross-sectional view showing that the key structure in FIG. 3 is pressed. The elastic piece 30 is disposed in the center of the back surface of the keycap 50. A plurality of posts 52 protruding from the back surface, under the key cap, of the keycap 50 are located to align with guiding holes 141 of the base 10. Guiding surfaces 1412 in the guiding holes 141 are used to guide the posts 52 to be inserted into the guiding holes 141. The posts 52 are brought into contact with ribs 1411 inside the guiding holes 141 respectively, while hooks 54 are engaged with engaging portions 142 of the base 10. As shown in FIG. 3, when the user presses a finger-pad, or pressing portion 51 of the keycap 50, each of the posts 52 moves along the rib 1411 inside the guiding hole 141 toward a body 11, so that the hooks 54 are not engaged with the engaging portion 142, thereby causing the abutting post 56 to move toward the body 11. As shown in FIG. 4, when the user release his finger and does not press the pressing portion 51, the elastic piece 30 pushes the abutting post 56 to cause the abutting post 56 to move reversely. In this way, each of the posts 52 can move reversely along the rib 1411 inside the guiding hole 141. Then, the hooks 54 are engaged with the engaging portions 142, thereby limiting the moving distance of the post 52 within the guiding hole 141. Thus, the keycap 50 can be prevented from escaping from the base 10.
However, the above-mentioned key structure has some problems as follows: (1) Since the keycap 50 is located above the base 10, the combination of the keycap 50 and the base 10 makes the total thickness of the key structure is at least the sum of thickness of the keycap 50 and the base 10. Thus, it is not easy to reduce the total thickness of the key structure. (2) The back surface of the keycap 50 is provided with four posts 52, two hooks 54, and an abutting portion 56. Accordingly, the base 10 has to be provided with four guiding holes 141 and two engaging portions 142. Each of these members is of a certain height and width, so that the whole key structure is complicated in construction. Thus, the friction forces among these members and the time for assembling the key structure are increased inevitably, which does not conform to the tendency toward the miniaturization of the key structure. (3) When the user intends to press the keycap 50, the user has to overcome the friction force between the keycap 50 and the base 10, so that the user has to apply a larger force to press the keycap 50 completely, which does not conform to the requirement for ergonomics. Therefore, it is an important issue for the manufacturers in this art to develop a keyboard for easy assembly and use.
In view of the above, the present Inventor proposes a thin key structure capable of reducing the total thickness and weight of the key structure, whereby the key structure becomes more compact and user-friendly to generate a steady operation.